Process of recovering metals from ores.



- 1,291,824. Patented 1311.211919.

R. GAHL.

PROCESS 0F RECOVERING METALS FROM ORES.

APPLICATION min Nov. e.' 1911. v

mamada-m Tosmd Jan/mz@ @not "cul/ RUDOLF GAHL, OF MIAMI, ARIZONA.

PROCESS OF RECOVERING METALS FROM ORES.

Specification of Letters Patent.

Patented Jan. 21, 1919.

Application led November B, 1917. Serial No. 200,931.

To all whom t may concern:

Be it known that I, RUDOLF GAHL, a citizen of the United States,residingat Miami, in the county of Gila and State of Arizona, have inventedcertain new and useful Inlprovements in Processes of Recovering Metalsfrom Ores, of which the following is a specification.

My invention relates to a process of recovering metals from ores. Forthe beneficiation of certain ores, especially porphyry copper ores bymeans of concentration processes, very line grinding is necessary toliberate the economic mineral from the gangue particles and fromparticles'of such minerals as cannot be recovered by the concentrationprocess. The cost of grinding, therefore, often constitutes theheaviestitem of the reduction cost by the processes in' question.

For this and other reasons, it has been customary to reduce thegrindingexpense by not attempting to carry the grinding as far as isnecessary for freeing all mineral from gangue particles, but to applythe concentrating process to what may be called insufliciently crushedore. The products which the concentration' process yields in this caseare so-called concentrate containing essentially those mineral particlesthat have been liberated largely from the gangue and a middling productcontaining particles consisting of gangue and mineral combined, inaddition to a 'waste product called tailing,

It has been customary in such cases to i regrind the middling productand -then to l attempt another concentration.

s high-grade product.

While the procedure just described has been successful in a measure, itdoes not permit essentially completerecovery of the mineral contents ofthe. ore in the form of a y The two principal causes for thisshortcoming-are (1) a great number of insufliciently round particlesfind 'their way into the tailing` product instead of going'into themiddling product; and '(2) the-treatment of the reground middlingproduct by a concentration process is rarely satisfactory, inasmuch asthe resulting tailing,I always carries `high mineral values.V The reasonseems'to lie in the fact that altered or partly decomposed mineralsleaching,

4which the Slime has which offer difficulties in concentration processesaccumulate to some extent in the middling product.

In speaking of concentration processes so far, I have been referring togravity concentration processes only. As a matter of fact, the flotationprocess which has recently come into use is also a concentrationprocess..

In applying the flotation process, metallurgists have .generallyconfined themselves to applying the s a-me to slimes, i. e., very finecrushed ortions of ore; or when they have applied 1t to ore ulps as aWhole, i., c., sand and slime mixed), have specified that the crushingshould be very fine.

I have discovered, however, that the flotation process may be so carriedout that it is Well adapted to the treatment of insulliciently crushedore, and that when so applied, in the manner hereinafter described.

there will be produced, in c'ontradistinction to the gravity process, atailing product practically free from mineralvalues, while the flotationconcentrates contain mineral particles essentially free from gangue andthe middlings contain mineral particles com-- bined with the'gangue. Theseparation into these three products is not necessarily made in oneoperation. As in the example quoted below, the first flotation may, forinstance. separate out the concentrate and an additional treatment ofthe balance of the pulp result in the middling` and tailing product.

" My experience is further, that flotation, .l like the gravityconcentration process, does' not permit the separation of the middling'lproduct into a mineral free secondarytailing product and' a high-gradesecondary concentrate Vproduct even after regrinding. On the other hand,I have discovered that the middling product can be obtained in agranular form suitable forY roasting an if the flotation in which themiddlng is produced is ap lied to a pulp from lbeen previously removedby means known to the art, as for instance, a' drag classifier. Suchroastmg treatment followed by leaching permits a high extraction of thevalues contained in the middlings product. y It has been mentionedbefore that. the

flotation' process will produce a telling prtduct practically frommineral 35 leaching with sulfuric per, 0.3% being in oxid combination.

values in addition to a concentrate and a middling productA refractorylto further treatment by dotation. The term practically :tree frommineral values is meant to `apply only to such mineral values as areamendable to dotation. YWhere, for instance, oxidized copper ores aretreated it' is only possible to remove the copper suldds with a veryhigh degree of extraction, While the copper carbonates are extracted toa smaller` extent, and silicates to a smaller extent yet. Where the oxidminerals 'exist in a suiiciently large percentage, another method mayhave to be used to supplement the flotation treatment, and l preferleaching for this purpose.

As an example of my process, a copper A ore was ground so thatpractically all the product was fine enough to pass a 48-inesh screen,Which though comparatively une grinding is by n o means ysufficient toliber- `ate all the mineralparticles.' 'llhe ore treated containedapproximately 1.5% cogs the result of a combined gravity and iotatlonconcentration, a concentrate contain- 111%` abou.t 30% of copper wasproduced.

he tailings Jfrom thls concentration proc# ess, which would ordinarilybe considered Waste product, were then, after the removal separated intoa middling and ofthe slime, telling product in a dotation machine.

While thel material fed to this dotation inachlne carried 0.26% copper,the tailing product contained only 0.11% copp', and .after acidcontained only 0.04% copper. y I

The middling product, containing 1.70% cop er was roasted with salt andthen leac ed with sulfuric acid, and by this process the copper contentreduced to 0.09% copper. ln other Words, the loss originating from thisWaste product was also very small. 'l`l1ecopper solutions produced byleaching the tailings and .by leaching the roasted mlddlings can then betreated either by preoipitating the copper on iron to produce cementcopper, or by electrolytic deposition. The attached gure represents partont a of the residue wask nennen@ dlings produced `by flotation in thisniachine are sent to a roasting furnace in which lthey are Igwen akchloridizing roast,

this otv sheet, ltere, feeders,

and then together with the unroasted tailp ings sent to the leachingplant. From the resulting solutions, the copper is recovered either byprecipitation as cement copper or.

as electrolytic copper, and the residues from the leaching arediscarded.

' The slimed product from the desliming classier may he treated in anyof the Well known Ways.

i claim:

1.l The process oi treating ores which consists in subjecting desliinedpulp to @otation to produce .a nriddling product, roasting the middlingproduct, :and leaching the roasted product to obtain a metalliieroussolution.

2. rlhe process oit treatings ores which vcon-l siste in subjectingdeslinied pnl to dotation to produce a nciddling pro uct, roast ing. themiddling product., and leaching the roasted product and `the tailings toobtain a metallilerous'solution.,

3. The process of treating ores which consists in lsubjecting desliniedpulp to @otation to produce concentrates and tailings,

subjecting such tailings to dotation to prol ducea middling product,roasting the iniddlin product, and leaching the roasted prodguct toobtain a metalliierous selution. 4l. The process as claimed1 inl claim 31ncludingthe step of also lea-ching the tailings trom the :flotationprocess in which the middling product was obtained.

. lin testimony whereof l iny signature.

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